As a device for visualizing the configuration of a specimen with precision of nm (nanometer), there are a SEM (scanning electron microscope), a STEM (scanning transmission electron microscope), and a TEM (transmission electron microscope). The SEM and STEM are devices that raster-scans the specimen with an electron beam that has been converged to the order of nm, detects a signal that is generated from an electron beam irradiated area, and synchronizes the signal with raster scanning to form an image. The TEM is a device that irradiates parallel electron beams to the specimen, and enlarges and projects electrons that have been transmitted through the specimen on a camera or a fluorescence plate by an electromagnetic lens for observation. In recent years, with the miniaturization of the semiconductor device structure, there increase needs for the management of dimensions of several tens nm width which is conducted by the high-resolution SEM, and the management of dimensions of several nm width which is conducted by the STEM, that is, for the dimension management using an image of an intermediate or high magnification or a defect inspection in the middle or high magnification. In order to accurately obtain the dimension of the specimen or the configuration of a defect on the basis of the image that has been obtained by those devices, an accurate magnification of the image with respect to the specimen is required. JP-A 2006-058210 discloses a high-precision magnification correcting technique. In the technique, the magnification with respect to the specimen is corrected by using a standard specimen including a repetitive pattern having a known cycle. A first image obtained by actually measuring a magnification of the image with respect to the specimen is recorded by using a specimen having a microscopic structure, a second image whose magnification with respect to the specimen is unknown is recorded, and the magnification of the second image with respect to the first image is analyzed by the aid of an image analysis. The magnification of the second image with respect to the specimen is obtained on the basis of the magnification of the first image with respect to the specimen and the magnification of the second image with respect to the first image. Hereinafter, the above magnification analysis is repeated with the second image as the first image, to thereby measure the magnification in the entire magnification range.
It is assumed in JP-A 2006-058210 that the magnification within the image surface is uniform, and there is no geometric distortion. However, there actually exist diverse factors that geometrically distort the image. Specifically, there are the distortion that is attributable to a change in the height of the specimen or a change in the returning electric field as disclosed in JP-A 2000-040481, the distortion that is attributable to the distortion aberration as disclosed in JP-A 2002-184336, and the deflection distortion as disclosed in JP-A 2002-251975.
As a technique for measuring the above-mentioned geometric distortion, JP-A 2003-022773 discloses a technique by which a mark pattern having a two-dimensional cyclic structure of 200 nm cycle is used, electron beams are scanned with an angle with respect to the mark pattern to generate an interference pattern, and a geometric distortion is measured and corrected on the basis of the interference pattern. As the technique for correcting the geometric distortion, JP-A 2002-184336 discloses a technique by which the geometric distortion that is attributable to the change in the height of the specimen or the change in the returning electric field is measured by the aid of a standard mark, a correction data table is produced on the basis of the measured geometric distortion, and the electron beam scanning is controlled on the basis of the correction data table to correct the geometric distortion. Also, JP-A 2000-040481 discloses a technique by which the distortion that is attributable to the distortion aberration of an electronic optical lens is measured by means of a specimen having an orthogonal line that is about 5 μm to 0.5 μm in the line width, and corrected by a correction lens.